[shuttertalk]

I've always wondered how scratches on the front element of a lens affected image quality, and to a certain extent even dust and smudges. For example - ever looked at a second hand lens and debated whether to buy it because of noticeable scratches or marks on the glass?

Well this guy gets practical in testing the scenarios above out - from smudges to "dirt" and dust, to actually scratching his zoom lens, and for the final test - breaking the front element altogether. At each stage he takes photos and pixel peeps to see if the image quality is affected.

I won't ruin it for you but very interesting reading indeed...

http://kurtmunger.com/dirty_lens_articleid35.html

[Toad]

Interesting and completely in keeping with what I have always suspected...

The same cannot be said about dust or scratches on sensors however, which are completely visible even to an untrained eye.